Teleost NOD-like receptors and their downstream signaling pathways: A brief review

Nucleotide-binding oligomerization domain-like receptors (NOD-like receptors or NLRs) are key members of the immune system that act as intracellular sentinels. These pathogen recognition receptors are essentially characterized by a central nucleotide binding domain and a C-terminal leucine rich repeat domain responsible for recognition of pathogens. Over the past decade, our understanding of teleosts' NLRs has enhanced significantly although the signaling pathways remain to be elucidated. In this brief review, we have tried to decipher the structural and functional aspects of NLRs in teleost. The review also engages in illustrating the various downstream signaling pathways/molecules reported so far in fishes that enable the NLRs to act as important players in immune responses and defense mechanisms against pathogens. Importantly, we try to explore the lacunae in structural and mechanistic details of NLRs in the teleost that would help in identifying key areas in which research is needed to complete our understanding of NLRs and their structural and functional evolution.